Expression Of Postsynaptic Density-95 Research Articles

Tanshinone IIA Regulates Synaptic Plasticity in Mg2+-Free-Induced Epileptic Hippocampal Neurons via the PI3K/Akt Signaling Pathway.

Tanshinone IIA (TSIIA) is an element of the effective ingredients of Salvia miltiorrhiza Bunge (Labiatae), exhibits a significant therapeutic effect in brain neuroprotection. The focus of this study was the examination of synaptic plasticity of in Mg2+-free-induced epileptic hippocampus neurons and how TSIIA protects against it. The purity of the primary hippocampal neurons extracted from Sprague Dawley rats was assessed within 24 hours by microtubule-associated protein (MAP2) immunofluorescence staining. A hippocampal neuron model for Mg2+-free-induced spontaneous recurrent epileptiform discharge was developed, five experimental groups were then randomized: blank (Blank), model (Model), TSIIA (TSIIA, 20 µM), LY294002 (LY294002, 25 µM), and TSIIA+LY294002 (TSIIA+LY294002, 20 µM+25 µM). FIJI software was used to examine variations of neurite complexity, total length of hippocampal neurons, number of primary dendrites and density of dendritic spines. Developmental regulation brain protein (Drebrin) and brain-derived neurotrophic factor (BDNF) expression was evaluated using immunofluorescence staining and the relative expression of phospho-protein kinase B (p-Akt)/Akt, BDNF, synaptophysin (SYN) and postsynaptic density 95 (PSD-95) determined by Western blot. In contrast to the model group, TSIIA drastically reduced damage to synaptic plasticity of hippocampal neurons caused by epilepsy (p < 0.05). The TSIIA group showed a significant increase in the relative expression of PSD-95, SYN, BDNF, and p-Akt/Akt (p < 0.01). TSIIA was effective in reducing harm to the synaptic plasticity of hippocampal neurons induced by persistent status epilepticus, with the possible mechanism being regulation of the phosphatidylinositol 3-kinase 56 (PI3K)/Akt signaling pathway.

How Tongxie-Yaofang Regulates Intestinal Synaptic Plasticity by Activating Enteric Glial Cells and NGF/TrkA Pathway in Diarrhea-Predominant Irritable Bowel Syndrome Rats.

Diarrhea-predominant irritable bowel syndrome (D-IBS) is a frequent functional gastrointestinal disease that affects health and quality of life owing to its high incidence and recurrence rate. Tongxie-Yaofang (TXYF) is a traditional Chinese medicine prescribed for D-IBS. However, the therapeutic mechanism of TXYF has not been fully elucidated. This study aimed to investigate the effects of TXYF on visceral hypersensitivity in stress-induced D-IBS rats and the underlying mechanisms. Electromyographic (EMG) activity of the external oblique muscles and the abdominal withdrawal reflex (AWR) score captured by Barostat were used to quantify the effect of TXYF on visceral sensitivity. Transmission electron microscopy (TEM) was used to observe the ultrastructure of the enteric nervous system (ENS). For molecular detection, the colonic expression of enteric glial cell's (EGC's) activation markers, glial fibrillary acidic protein (GFAP) and calcium-binding protein S100β, NGF, TrkA, synaptic plasticity-related factors, synaptophysin (SYN) and postsynaptic density-95 (PSD-95), glutamate, glutamate receptors α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor (AMPAR), and N-methyl-D-aspartate receptor (NMDAR) were detected by immunohistochemistry, enzyme-linked immunosorbent assay, and real-time PCR. An ex vivo experiment was conducted to measure the EGC-induced NGF release. TXYF decreased the EMG activity and AWR scores in rats with D-IBS. Under TEM, TXYF improved the dense and irregular nerve arrangement, narrowed the synaptic cleft, and decreased the number of synaptic vesicles in D-IBS rats. In addition, TXYF decreased the expression of GFAP, S100β, SYN, and PSD-95; down-regulated the levels of NGF, TrkA, and glutamate; and reduced the mRNA expression of AMPAR1, NMDAR1, and NMDAR2B. In an ex vivo experiment, TXYF decreased NGF release in D-IBS rats, and this trend disappeared under EGC inhibition. TXYF alleviated visceral hypersensitivity in D-IBS rats possibly by improving synaptic plasticity through inhibiting the activity of EGCs and the NGF/TrkA signaling pathway in the colon.

Electroacupuncture alleviates PTSD-like behaviors by modulating hippocampal synaptic plasticity via Wnt/β-catenin signaling pathway

Abnormalities in hippocampal synaptic plasticity contribute to the pathogenesis of post-traumatic stress disorder (PTSD). The Wnt/β-catenin signaling pathway is critical for the regulation of synaptic plasticity. PTSD symptoms can be alleviated by correcting impaired neural plasticity in the hippocampus (Hipp). Electroacupuncture (EA) has a therapeutic effect by relieving PTSD-like behaviors. However, little is known about whether the Wnt/β-catenin pathway is involved in EA-mediated improvements of PTSD symptoms. In this study, we found that enhanced single prolonged stress (ESPS)-induced PTSD led to abnormal neural plasticity, characterized by the decline of dendritic spines, the expression of postsynaptic density 95 (PSD95), and synaptophysin (Syn) in the stressed Hipp along with the reduction of Wnt3a and β-catenin, and increased GSK-3β. EA significantly alleviated PTSD-like behaviors, as assessed by the open field test, elevated platform maze test and conditioning fear test. This was paralleled by correcting abnormal neural plasticity by promoting the expression of PSD95 and Syn, as well as the number of dendritic spines in the Hipp. Importantly, EA exerted anti-PTSD effects by augmenting the expression levels of Wnt3a and β-catenin, and decreasing that of GSK-3β. The effects mediated by EA were abolished by XAV939, an inhibitor of the Wnt/β-catenin pathway. This suggests that EA relieved ESPS-induced PTSD-like behaviors, which can largely be ascribed to impaired neural plasticity in the Hipp. These findings provide new insights into possible mechanisms linking neural plasticity in the Hipp as potential novel targets for PTSD treatment in EA therapy.

Effect of Xiaoxuming Decoction on synaptic plasticity following acute cerebral ischemia-reperfusion in rats

This study aims to explore the effect of Xiaoxuming Decoction on synaptic plasticity in rats with acute cerebral ischemia-reperfusion. A rat model of cerebral ischemia-reperfusion injury was established by middle cerebral artery occlusion(MCAO). Rats were randomly assigned into a sham group, a MCAO group, and a Xiaoxuming Decoction(60 g·kg~(-1)·d~(-1)) group. The Longa score was rated to assess the neurological function of rats with cerebral ischemia for 1.5 h and reperfusion for 24 h. The 2,3,5-triphenyltetrazolium chloride(TTC) staining and hematoxylin-eosin(HE) staining were employed to observe the cerebral infarction and the pathological changes of brain tissue after cerebral ischemia, respectively. Transmission electron microscopy was employed to detect the structural changes of neurons and synapses in the ischemic penumbra, and immunofluorescence, Western blot to determine the expression of synaptophysin(SYN), neuronal nuclei(NEUN), and postsynaptic density 95(PSD95) in the ischemic penumbra. The experimental results showed that the modeling increased the Longa score and led to cerebral infarction after 24 h of ischemia-reperfusion. Compared with the model group, Xiaoxuming Decoction intervention significantly decreased the Longa score and reduced the formation of cerebral infarction area. The modeling led to the shrinking and vacuolar changes of nuclei in the brain tissue, disordered cell arrangement, and severe cortical ischemia-reperfusion injury, while the pathological damage in the Xiaoxuming Decoction group was mild. The modeling blurred the synaptic boundaries and broadened the synaptic gap, while such changes were recovered in the Xiaoxuming Decoction group. The modeling decreased the fluorescence intensity of NEUN and SYN, while the intensity in Xiaoxuming Decoction group was significantly higher than that in the model group. The expression of SYN and PSD95 in the ischemic penumbra was down-regulated in the model group, while such down-regulation can be alleviated by Xiaoxuming Decoction. In summary, Xiaoxuming Decoction may improve the synaptic plasticity of ischemic penumbra during acute cerebral ischemia-reperfusion by up-regulating the expression of SYN and PSD95.

Kai-Xin-San Improves Cognitive Impairment via Wnt/β-Catenin and IRE1/XBP1s Signalings in APP/PS1 Mice.

Alzheimer's disease (AD) is the most common type of dementia with an insidious onset and slow progression. Kai-Xin-San (KXS) has been reported to be effective in improving cognitive impairment in AD. However, the mechanism is still confused. In this study, we employed APP/PS1 mice to explore the neuroprotective mechanism of KXS. Forty-eight male APP/PS1 mice were randomly divided into model group, KXS groups (0.7, 1.4, and 2.8 g/kg/d, p.o.) and the wild-type mice were assigned to the normal control group (n = 12 in each group). Y-maze and novel object recognition tests were carried out after continuous intragastric administration for 2 months. The abilities of learning, memory, and new object recognition in the APP/PS1 mice were enhanced significantly after KXS treatment. KXS can reduce the deposition of Aβ40 and Aβ42 in APP/PS1 mice brain. KXS decreased the levels of serum inflammatory cytokines, tumor necrosis factor-α, interleukin-1β, and interleukin-6. KXS increased the activities of superoxide dismutase and glutathione peroxidase significantly, whereas it inhibited the contents of reactive oxygen species and malondialdehyde significantly. In addition, we also detected Wnt/β-catenin signaling related proteins, such as Wnt7a, β-catenin, low-density lipoprotein receptor-related protein 6 (LRP6), glycogen synthase kinase-3β (GSK-3β), nuclear factor kappa-B (NF-κB), postsynaptic density 95 (PSD95), microtubule associated protein-2 (MAP-2), and endoplasmic reticulum stress (IRE1 pathway) related proteins, such as inositol-requiring enzyme 1 (IRE1), phosphorylated IRE1(p-IRE1), spliced X-box-binding protein 1 (XBP1s), immunoglobulin binding protein (BIP), and protein disulfide isomerase (PDI) in the hippocampus. Results showed that KXS decreased the expression of GSK-3β, NF-kB, p-IRE1/IRE1 ratio, XBP1s, and BIP; increased the expression of Wnt7a, β-catenin, LRP6, PSD95, MAP2, and PDI. In conclusion, KXS improved cognitive impairment by activating Wnt/β-catenin signaling, inhibiting the IRE1/XBP1s pathway in APP/PS1 mice.

Intranasal administration of mitochondria alleviated cognitive impairments and mitochondrial dysfunction in the photothrombotic model of mPFC stroke in mice

ObjectivesDysfunction in mitochondrial activity may have profound role in ischemic stroke-induced neuronal death, hence maintaining the mitochondrial function seems to be valuable for neuronal viability and neurological improvement. MethodsC57BL/6J mice were allocated into sham and stroke groups. Mice in the stroke groups underwent photothrombosis-induced stroke in the medial prefrontal cortex (mPFC) and were divided into the following subgroups; RB, Mito 85, Mito 170, and Mito 340, and received their respective treatments via intra-nasal route every other day (3 days per week) for one week. A battery of behavioral tests including social interaction, passive avoidance, and the Lashley III maze was used to investigate social, contextual, and spatial memories. Moreover, changes in mitochondrial function, including reactive oxygen species (ROS) and ATP levels, and mitochondrial membrane potential, were assessed in mPFC. The expression of growth-associated protein 43 (GAP-43), post-synaptic density-95 (PSD-95), and synaptophysin (SYP) was detected by western blotting. ResultsBehavioral results revealed that mitotherapy alleviated ischemia-induced memory impairment. Also, transplantation of exogenous mitochondria lowered ROS, restored ATP generation, and improved mitochondrial membrane potential. Induction of ischemia decreased the levels of synaptic markers in mPFC while exogenous mitochondria (170 and 340µg) significantly upregulated the expression of GAP-43 and PSD-95 after ischemic stroke. ConclusionOur research highlighted the importance of mitotherapy in regulating synaptic markers expression and mitochondria function, which could represent a potential strategy for improving cognitive and memory deficits following stroke.

Hippocampal synaptic dysfunction and spatial memory impairment in omeprazole-treated rats.

Although the association of prolonged use of proton pump inhibitors, such as omeprazole, with memory impairment has been reported more than two decades ago, its underlying molecular mechanism is yet to be determined. Thus, in this study, we aimed to determine the mechanisms underlying the effect of prolonged omeprazole treatment on hippocampal synaptic function and spatial memory in male rats. Adult rats were subcutaneously administered with omeprazole for 12 or 24 weeks. Spatial memory was assessed using the Morris water maze (MWM) test. We examined the hippocampal protein expression of synaptic plasticity proteins, including the AMPA receptor subunit GluA1, postsynaptic density-95 (PSD-95), and activity-regulated cytoskeleton-associated protein (Arc), and the hippocampal expression and localization of androgen receptor (AR). In the MWM test, the escape latency was found to be significantly higher, and the number of platform crossings and the time spent in the target quadrant were significantly lower in the rats treated with omeprazole compared to the control rats. Hypomagnesemia and lower bone and brain Mg2+ content were also detected in the omeprazole-treated groups compared with the control group. The expression of GluA1, PSD-95, and Arc in the hippocampus and the expression of AR in the dentate gyrus and CA1 of the hippocampus were significantly lower in the omeprazole-treated groups than in the control group. These results suggest that prolonged omeprazole treatment might lead to memory deficit by impairing glutamate receptor trafficking or synaptic anchoring. Hypomagnesemia and brain Mg2+ deficiency may be, at least in part, involved in omeprazole-induced memory impairment.

Chronic orexin-1 receptor blockage attenuates depressive behaviors and provokes PSD-95 expression in a rat model of depression

Depression is a devastating mood disorder affecting more than 300 million people worldwide. Almost 30 % of patients still suffer from treatment resistant depression. Although many reports support the involvement of orexin in the pathophysiology of depression, the precise role of orexin is still unclear. In this study, we evaluated the role of the orexin 1 receptor (Orx1R) on depressive behaviors and the alterations in postsynaptic density-95 (PSD-95) protein in the chronic mild stress (CMS) model of depression. Fifty-four male Wistar rats were randomly allocated to 6 groups; Control, CMS, acute SB-334867 (SB), CMS+SB, chronic SB (CSB) and CMS+CSB. Rats were exposed to one or two unpredictable stressors each day for three weeks for the induction of CMS. Intracerebroventricular (icv) injection of SB-334867, a selective Orx1R antagonist, was performed either 30 min before behavioral tests (acute) or once daily for 14 days (chronic). Behavioral despair was assessed by immobility time in the forced swim test (FST), sucrose consumption in sucrose preference test (SPT), and the number of crosses in the open field test (OFT) on days 1, 11, and 22 of the experiment. Finally, rats were decapitated, and brain tissue of the hippocampus (HPC) and prefrontal cortex (PFC) were collected, and the relative expression of PSD-95 was evaluated by western blotting. The CMS model rats showed a significant increase in FST immobility time (P = 0.001) and a decrease in locomotion (P = 0.04) and sucrose preference (P = 0.039). Chronic application of SB decreased immobility time to the control values (P = 0.001) and diminished locomotion (P = 0.047) and sucrose preference (P = 0.042) in comparison to the CMS group. Acute SB reversed just the immobility time (P ≤ 0.006). Chronic SB treatment increased the relative PSD-95 expression in PFC (P = 0.001). Hence, chronic antagonism of Orx1R alleviates depressive behaviors induced by CMS and improves PSD-95 expression in PFC.

Advanced maternal age impairs synaptic plasticity in offspring rats

Advanced maternal age (AMA) has become more common in the last decade and is associated with poor neurodevelopmental outcomes in offspring. Neurocognitive and emotional development is associated with synaptic structural and functional plasticity. In the present study, we investigated the relationship between AMA and synapse plasticity in the offspring. We examined the synaptic ultrastructure, synapse-related proteins and long-term potentiation (LTP) in the offspring of Sprague–Dawley female rats aged 12 months (AMA group) and 3 months (Control group) on postnatal (P) days 7, 14, 28 and 60. Immunofluorescence analysis revealed decreases in the expression of neurofilament 200 (NF200) and axon length in the AMA group compared with the control group at P14. Western blot analysis showed that the expression of postsynaptic density-95 (PSD-95) and synaptophysin (SYP) was reduced in the immature offspring of the AMA group at P7. Transmission electron microscopy showed decreased thickness of the PSD and increased length of the active zone (AZ) in the offspring of the AMA group. Electrophysiological recordings in hippocampal slices revealed impaired LTP in the AMA offspring. Our data suggest that AMA impairs the synaptic plasticity of offspring, which may underlie the mechanism of neurodevelopmental disorders.

Effect Of Aerobic Exercise On The Learning And Memorizing Abilities And Hippocampal Psd-95 In Depressive Rats

PURPOSE: 4 weeks of CUMS (Chronic Unpredictable Mild Stress) was to build depressive rats and investigate the effect of an aerobic exercise intervention on hippocampal PSD-95 (postsynaptic density-95) expression and spatial learning and memorizing ability. METHODS: 30 male SD rats randomly divided into 3 groups: the Control group (C), the Model group (M), and the Exercise group (E). M and E were subjected to CUMS stimulation and/or aerobic exercise for 4 weeks respectively. E received swimming training for 4 weeks (60 min/day, 6 days/week). OFT was used to test CUMS related anxiety-like behavior in order to detect the success of model. MWM was performed to evaluate their spatial learning and memorizing ability. The expression of PSD-95 was tested by RT-PCR and WB. The experimental data was reported as mean ± SE. A statistical significant level was defined when P < 0.05. RESULTS: 1) OFT: CUMS can decrease the central zone duration and exercise alleviates anxiety-like behavior (C:16.02 ± 7.96; M:8.3 ± 1.25; E:22.61 ± 10.7, P < 0.05); 2)MWM detection: during 6 days of the navigation experiment, M showed more difficulty to find the platform compared with C and E(P < 0.05), while there was no significant difference between C and E (P > 0.05); During the space exploring experiment, M spent much time to find the platform compared with C and E (C:3.14 ± 0.38; M:1.57 ± 0.79; E:2.57 ± 0.53, P < 0.05); 3) mRNA and protein detection: compared with C, the mRNA(C:1.29 ± 0.39; M:0.56 ± 0.19; E:1.21 ± 0.11) and protein level of PSD-95 (C:0.99 ± 0.05; M:0.77 ± 0.05; E:1.19 ± 0.09) significantly decreased in group M, while increased in group E(P < 0.05). CONCLUSIONS: 4 weeks of aerobic exercise intervention effectively reverses the depression symptoms and improves their spatial learning and memorizing ability in rats pretreated by CUMS stimulation. In addition, aerobic exercise can rescue and significantly up-regulate the expression of PSD-95 in hippocampus which suppressed by CUMS stimulation. In summary, this study demonstrated the improvement of CUMS-associated learning and memorizing ability by exercise via enhanced expression of PSD-95 in hippocampus.

MiR-132 downregulation alleviates behavioral impairment of rats exposed to single prolonged stress, reduces the level of apoptosis in PFC, and upregulates the expression of MeCP2 and BDNF

Post-traumatic stress disorder (PTSD) is usually accompanied by anxiety symptoms and decreased expression of brain-derived neurotrophic factor (BDNF), which played an important role in promoting neuronal proliferation and survival. Methyl CpG-binding protein 2 (MeCP2) is a positive mediator of BDNF and is regulated by miR-132-3p. In the present study, we explored the possible molecular mechanism of miR-132, focusing on the involvement of MeCP2 and BDNF in the formation of anxiety-like symptoms of PTSD. Single prolonged stress (SPS) was used to establish a model of PTSD in adult rats and the anxiety-like behavior was tested by the elevated plus-maze (EPM). The level of miR-132 in the prefrontal cortex (PFC) was increased and intraventricular injection of anti-miR-132 could significantly improve the anxiety-like behavior of rats exposed to SPS through MeCP2 and the subsequent upregulation of BDNF levels. Then tropomyosin-related kinase B (TrkB) and downstream signals, including MAP kinase ERK1/2 and phosphoinositol 3-kinase (PI3K)/Akt pathways, were activated by BDNF upregulation, and might participate in regulating dendritic complexity and the expression of postsynaptic density-95 (PSD95) and synapsin I in the PFC of SPS rats. Furthermore, we found that the apoptosis of cells in PFC induced by SPS procedure could be alleviated by miR-132 inhibition. Our results suggest that miR-132 might be involved in the formation of anxiety-like symptoms of adult rat PTSD models by targeting MeCP2, and this effect is related to BDNF/TrkB and its downstream ERK and Akt signaling pathways.

The Neuroprotective Effects of Astragaloside IV against H2O2-Induced Damage in SH-SY5Y Cells are Associated with Synaptic Plasticity

The aim of this study was to investigate whether the neuroprotective effects of astragaloside IV (AS-IV) against hydrogen peroxide (H2O2)-induced damage on human neuroblastoma cell line (SH-SY5Y) are associated with synaptic plasticity. The concentration screening of AS-IV and H2O2 on SH-SY5Y cells and the protective effects of AS-IV on SH-SY5Y cells under H2O2 stress were all determined by MTT assay. The expression of postsynaptic density 95 (PSD-95) and growth-associated protein 43 (GAP-43) were measured by western blot (WB) and inmunofluorescence staining assay under the same treatment conditions. According to the MTT results, the concentration of H2O2 at 50 μmol/L for 3 h was used for the cell damage model, and various concentrations of AS-IV (0.1, 0.2, 0.3, and 0.4 μmol/L) were used to affect SH-SY5Y cells. The MTT results showed that pretreatment of SH-SY5Y cells with AS-IV (0.1, 0.2, 0.3, and 0.4 μmol/L) attenuated the damage induced by H2O2 (50 μmol/L, 51.62% cell viability) and increased cell viability to 64.19, 63.48, 65.86, and 65.81%, respectively. Western blot analysis and immunofluorescence staining showed that the protective effects of AS-IV against SH-SY5Y cell damage caused by H2O2 resulted in reduced expression of PSD-95 and increased expression of GAP-43 in comparison with the H2O2 treatment group. The conclusion shows that AS-IV protected SH-SY5Y cells and enhanced their viability under H2O2 stress. AS-IV may facilitate presynaptic and postsynaptic plasticity to exert protective effects against oxidative damage of SH-SY5Y cells.

Effects of electroacupuncture at "Baihui" and "Yongquan" on the levels of synaptic plasticity related proteins postsynaptic density-95 and synaptophysin in hippocampus of APP/PS1 mice

From the perspective of β-amyloid (Aβ) toxicity and synaptic plasticity, the mechanism of electroacupuncture to improve learning and memory ability in the early pathological stages of Alzheimer's disease was explored. Twelve male amyloid-protein precursor (APP)/γ-secretase (PS1) double transgenic AD mice were randomly and equally divided into electroacupuncture (EA) group and model group, and other 6 male C57BL/6 mice were used as the normal group. EA (1 Hz/50 Hz, 0.5 mA) was applied to "Baihui" (GV20) and bilateral "Yongquan"(KI1) for 15 min, once every other day for 6 weeks. Immunofluorescence was used to observe the positive expression of Aβ in the left hippocampus. Immunohistochemistry was used to observe the positive expression of postsynaptic density-95 (PSD-95) in the left hippocampus. Western blot was used to detect the expression of PSD-95 and synaptophysin (SYN)in the right hippocampus. Immunofluorescence results showed that extracellular Aβ was seen in the model group and electroacupuncture group, but no senile plaques were seen. Compared with the normal group, the expression level of Aβ in the hippocampus of the model group increased significantly (P<0.01). Compared with the model group, the expression of Aβ in the hippocampus of the EA group decreased (P<0.05). Immunohistochemical results showed that compared with the normal group, the PSD-95 positive expression in the model group was decreased(P<0.05). Compared with the model group, the expression of PSD-95 in the EA group was increased (P<0.05). Western blot results showed that compared with the normal group, the expression levels of PSD-95 and SYN in the hippocampus of the model group were decreased (P<0.05, P<0.01). Compared with the model group, the expression levels of PSD-95 and SYN in the EA group were increased (P<0.05，P <0.01). EA can reduce the expression of Aβ in the hippocampus of APP/PS1 mice and increase the expression of PSD-95 and SYN, which may contribute to its effect in improving the synaptic plasticity.

Effects of early postnatal exposure to fine particulate matter on emotional and cognitive development and structural synaptic plasticity in immature and mature rats.

IntroductionFine particulate matter (PM2.5) is closely associated with many neurological disorders including neurodegenerative disease, stroke, and brain tumors. However, the toxic effects of PM2.5 on neurodevelopment remain unclear. In this study, we aimed to determine the neurotoxic effects of early postnatal exposure to PM2.5 in immature and mature rats.MethodsWe exposed neonatal rats to PM2.5 (2 or 10 mg/kg body weight) through intranasal instillation from postnatal day (PND) 3–15, once a day. Emotional and cognitive development were evaluated using the elevated plus maze, forced swimming, and Morris water maze tests. Hippocampal tissue was collected and subjected to transmission electron microscopy observation and western blot analysis.ResultsRats had lower body weight after exposure to high dose of PM2.5. The behavioral test results indicated that high‐dose PM2.5 exposure led to increased anxiety‐like symptoms in immature and mature rats, apparent depressive‐like behaviors in mature rats, and impaired spatial learning and memory abilities in immature rats, and low‐dose PM2.5 exposure increased anxiety‐like behaviors in immature rats. Further, high‐dose PM2.5 exposure contributed to fewer synapses, thinner postsynaptic density, and shorter active zone in immature and mature rats, and also decreased expressions of synaptophysin (SYP), growth associated protein‐43 (GAP43), and postsynaptic density‐95 (PSD95) in immature rats, SYP and PSD95 in mature rats. Moreover, low‐dose PM2.5 exposure diminished the expression of PSD95 in immature rats. In addition, high‐dose PM2.5 exposure reduced brain‐derived neurotrophic factor (BDNF) expression and cAMP response element binding protein (CREB) phosphorylation in both immature and mature rats, and low‐dose PM2.5 exposure lessened BDNF expression and CREB phosphorylation in immature rats.ConclusionsOur findings indicate that PM2.5 impairs emotional and cognitive development by disrupting structural synaptic plasticity, possibly via the CREB/BDNF signaling pathway.

Electroacupuncture Improves Synaptic Function in SAMP8 Mice Probably via Inhibition of the AMPK/eEF2K/eEF2 Signaling Pathway.

Synaptic loss and dysfunction is associated with cognitive impairment in Alzheimer's disease (AD). Recent evidence indicates that the AMP-activated protein kinase (AMPK)/eukaryotic elongation factor-2 kinase (eEF2K)/eukaryotic elongation factor-2 (eEF2) pathway was implicated in synaptic plasticity in AD. Therapeutic strategies for AD treatment are currently limited. Here, we investigate the effects of electroacupuncture (EA) on synaptic function and the AMPK/eEF2K/eEF2 signaling pathway in male senescence-accelerated mouse-prone 8 (SAMP8) mice. Male 7-month-old SAMP8 and SAMR1 mice (senescence-accelerated mouse resistant 1) were randomly divided into 3 groups: SAMR1 control group (Rc), SAMP8 control group (Pc), and SAMP8 electroacupuncture group (Pe). The Pe group was treated with EA for 30 days. Transmission electron microscopy (TEM) was used to observe the structure of synapse. The protein and mRNA expression of synaptophysin (SYN) and postsynaptic density 95 (PSD95) was examined by immunohistochemistry, western blot, and real-time RT-PCR. The activity of AMPK and eEF2K was studied by western blot. Our results showed that EA ameliorated synaptic loss, increased the expression of SYN and PSD95, and inhibited AMPK activation and eEF2K activity. Collectively, these findings suggested that the mechanisms of EA improving synaptic function in AD may be associated with the inhibition of the AMPK/eEF2K/eEF2 signaling pathway.

Enhanced Expression of the Key Mitosis Regulator Cyclin B1 Is Mediated by PDZ-Binding Kinase in Islets of Pregnant Mice.

The proliferation of pancreatic β cells is enhanced to enable an increase in β-cell mass and to compensate for insulin resistance during pregnancy. To elucidate the mechanisms involved, we previously investigated islets from pregnant and nonpregnant mice by gene expression profiling and found that the expression of postsynaptic density-95/Discs large/zonula occludens-1 (PDZ)–binding kinase (Pbk), a member of the mitogen-activated protein kinase kinase family, is increased in pregnant mouse islets compared with control mouse islets. Among the pregnancy hormones, treatment with estradiol upregulated Pbk expression. Inhibition of Pbk expression using a small interfering RNA for Pbk reduced bromodeoxyuridine incorporation in mouse insulinoma 6 cells, which was accompanied by a decreased expression of Ccnb1, a regulatory gene involved in mitosis. Ccnb1 expression was augmented in mouse islets during pregnancy. The forced expression of Pbk using an adenovirus system in isolated mouse islets increased Ccnb1 expression, and the Pbk inhibitor HI-TOPK-032 suppressed Ccnb1 expression in islets isolated from pregnant mice. Our results suggest that Pbk contributes to the expansion of islets during pregnancy and that Ccnb1 may assist Pbk in its role in β-cell proliferation.

Decreased post-synaptic density-95 protein expression on dendrites of newborn neurons following CX3CR1 modulation in the epileptogenic adult rodent brain

Temporal lobe seizures generate a large pool of new hippocampal neurons in the adult brain. Their role within the hyperexcitable neuronal network and how they are regulated by the immune response is unclear. Fractalkine and its receptor CX3CR1 constitute a chemokine pathway known to modulate the immune response in temporal lobe epilepsy. Here, 6 weeks of intracerebroventricular infusion of anti-CX3CR1 antibody, starting 1 week after electrically induced prolonged seizures in the temporal lobe (status epilepticus (SE)), reduced microglial activation within the hippocampus. This was associated with a several-fold decrease in expression of post-synaptic density-95 (PSD-95), a scaffolding protein specific for excitatory synapses on individual retroviral vector-mediated GFP-labeled hippocampal neurons at 6 weeks of age. In contrast, the scaffolding protein at inhibitory synapses, gephyrin, and related adhesion molecules were unaltered. These results indicate that expression of synaptic proteins on adult-born neurons in an epileptogenic environment is sensitive to the inflammatory milieu and may in turn affect excitation/inhibition balance.

Effects of Different Training Loads on Emotional State and mRNA and Protein Expressions of N-Methyl-D-Aspartate Receptor Subunits, Postsynaptic Density 95, and Kinesin Family Member 17 in Hippocampus of Rats.

BackgroundEmotional state can be affected by different training loads. The aim of this study was to explore the changes of rat emotional state, as well as the mRNA and protein expressions of N-methyl-D-aspartate receptors (NMDARs), postsynaptic density 95 (PSD-95), and kinesin family member 17 (KIF-17) in the hippocampus, by long-term moderate-intensity and high-intensity training models in rats.Material/MethodsThe exercise model of SD rats was set up by treadmill running of moderate and high intensities for 4 weeks. The rats in the moderate-intensity training group were given endurance training with increasing intensity, while rats in the high-intensity training group were given high-speed training, and those in the normal control group were also established. The body weights of rats were measured before and after exercise to determine weight reduction. Real-time PCR and Western blotting were used to detect the mRNA and protein expressions of NMDARs, PSD-95, and KIF-17 in hippocampus of rats under different training loads.ResultsCompared with the control group, the rats in the moderate-intensity training group had better body condition and emotional state, while the rats in the high-intensity training group had poor body condition and emotional state. The mRNA and protein expression of PSD-95, KIF-17, and NMDARs in the moderate-intensity training group were significantly elevated (P<0.05) while those in the high-intensity training group were suppressed (P<0.05).ConclusionsDifferent training loads have remarkable influences on the cognition, emotion, and mental status of rats, and can affect the mRNA and protein expressions of NMDARs, PSD-95, and KIF-17 in rats. Appropriate training loads alleviate hypoxia damage to the hippocampus, and also effectively improve hippocampus function.

The Role of Hippocampal Structural Synaptic Plasticity in Repetitive Transcranial Magnetic Stimulation to Improve Cognitive Function in Male SAMP8 Mice

Background: Repetitive transcranial magnetic stimulation (rTMS) has been used to improve cognitive function, but the stimulation protocols are variable and the underlying mechanism is unclear. Therefore, we intend to examine whether 5Hz rTMS with 30% maximum output could improve cognitive functions in senescence-accelerated-prone mouse 8 (SAMP8) through changing synaptic plasticity. Methods: SAMP8 and senescence-accelerated-prone mouse/resistant 1 (SAMR1) (7-month old male) were randomly divided into 3 groups: SMAP8 rTMS group (P8-rTMS), SMAP8 sham-rTMS group (P8-sham), and SAMR1 sham-rTMS group (R1-sham). The P8-rTMS group was treated daily with 5Hz rTMS with 30% maximum output for 14 consecutive days, whereas the other two groups were controls without rTMS stimulation. Morris water maze (MWM) experiment was performed after rTMS or sham treatment to assess the effect of rTMS on cognitive function. Reverse transcription polymerase chain reaction and Western blot assays were used to detect the mRNA and protein expression of presynaptic Synapsin (SYN) and postsynaptic density 95 (PSD95) in the hippocampus of these mice. Results: The mean escape latency of the P8-rTMS group was significantly shorter than that of the P8-sham group. The number of platform crossings of the P8-rTMS group was significantly higher than that of the P8-sham group. rTMS significantly upregulated the protein and mRNA expression of SYN and PSD95 in the hippocampus of p8-rTMS mice compared to those of P8 sham mice. Conclusion: 5Hz rTMS with 30% maximum output enhances learning and memory in the SAMP8 mice. This improvement may be associated with the increased expression of synaptic structure proteins SYN and PSD95 in the hippocampus.

Effects of Chronic Stress on Cognition in Male SAMP8 Mice

Background/Aims: Chronic stress can lead to cognitive impairment. Senescence-accelerated mouse prone 8 (SAMP8) is a naturally occurring animal model that is useful for investigating the neurological mechanisms of Alzheimer's disease. Here we investigated the impact and mechanisms of chronic stress on cognition in male SAMP8 mice. Methods: Male 6-month- old SAMP8 and SAMR1 (senescence-accelerated mouse resistant 1) mice strains were randomly divided into 4 groups. Mice in the unpredictable chronic mild stress (UCMS) groups were exposed to diverse stressors for 4 weeks. Then, these mice performed Morris water maze (MWM) test to assess the effect of UCMS on learning and memory. To explore the neurological mechanisms of UCMS on cognition in mice, we evaluated changes in the expression of postsynaptic density 95 (PSD95) and synaptophysin (SYN), which are essential proteins for synaptic plasticity. Five mice from each group were randomly chosen for reverse transcription polymerase chain reaction (RT-PCR) and western blotting analysis of SYN and PSD95. Results: The Morris water maze experiment revealed that the cognitive ability of the SAMP8 mice decreased with brain aging, and that chronic stress aggravated this cognitive deficit. In addition, chronic stress decreased the mRNA and protein expression of SYN and PSD95 in the hippocampus of the SAMP8 mice; however, the SAMR1 mice were unaffected. Conclusion: Our results demonstrate that decreased cognition and synaptic plasticity are related to aging. Moreover, we show that chronic stress aggravated this cognitive deficit and decreased SYN and PSD95 expression in the SAMP8 mice. Furthermore, the SAMP8 mice were more vulnerable to the detrimental effects of chronic stress on cognition than the SAMR1 mice. Our results suggest that the neurological mechanisms of chronic stress on cognition might be associated with a decrease in hippocampal SYN and PSD95 expression, which is critical for structural synaptic plasticity.